Eliminate spdlog dependency (#773)

Removes the vendored spdlog library (~12,000 lines) and replaces it with a purpose-built logging system in zencore (~1,800 lines). The new implementation provides the same functionality with fewer abstractions, no shared_ptr overhead, and full control over the logging pipeline.

### What changed

**New logging core in zencore/logging/:**
- LogMessage, Formatter, Sink, Logger, Registry - core abstractions matching spdlog's model but simplified
- AnsiColorStdoutSink - ANSI color console output (replaces spdlog stdout_color_sink)
- MsvcSink - OutputDebugString on Windows (replaces spdlog msvc_sink)
- AsyncSink - async logging via BlockingQueue worker thread (replaces spdlog async_logger)
- NullSink, MessageOnlyFormatter - utility types
- Thread-safe timestamp caching in formatters using RwLock

**Moved to zenutil/logging/:**
- FullFormatter - full log formatting with timestamp, logger name, level, source location, multiline alignment
- JsonFormatter - structured JSON log output
- RotatingFileSink - rotating file sink with atomic size tracking

**API changes:**
- Log levels are now an enum (LogLevel) instead of int, eliminating the zen::logging::level namespace
- LoggerRef no longer wraps shared_ptr - it holds a raw pointer with the registry owning lifetime
- Logger error handler is wired through Registry and propagated to all loggers on registration
- Logger::Log() now populates ThreadId on every message

**Cleanup:**
- Deleted thirdparty/spdlog/ entirely (110+ files)
- Deleted full_test_formatter (was ~80% duplicate of FullFormatter)
- Renamed snake_case classes to PascalCase (full_formatter -> FullFormatter, json_formatter -> JsonFormatter, sentry_sink -> SentrySink)
- Removed spdlog from xmake dependency graph

### Build / test impact

- zencore no longer depends on spdlog
- zenutil and zenvfs xmake.lua updated to drop spdlog dep
- zentelemetry xmake.lua updated to drop spdlog dep
- All existing tests pass, no test changes required beyond formatter class renames

1 files changed, 143 insertions, 185 deletions

diff --git a/src/zencore/logging.cpp b/src/zencore/logging.cpp
index ebd68de09..099518637 100644
--- a/src/zencore/logging.cpp
+++ b/src/zencore/logging.cpp
@@ -2,208 +2,128 @@
 
 #include "zencore/logging.h"
 
+#include <zencore/logging/ansicolorsink.h>
+#include <zencore/logging/logger.h>
+#include <zencore/logging/messageonlyformatter.h>
+#include <zencore/logging/nullsink.h>
+#include <zencore/logging/registry.h>
 #include <zencore/string.h>
 #include <zencore/testing.h>
 #include <zencore/thread.h>
 
 #include <zencore/memory/llm.h>
 
-ZEN_THIRD_PARTY_INCLUDES_START
-#include <spdlog/details/registry.h>
-#include <spdlog/sinks/null_sink.h>
-#include <spdlog/sinks/stdout_color_sinks.h>
-#include <spdlog/spdlog.h>
-ZEN_THIRD_PARTY_INCLUDES_END
+#include <mutex>
 
 #if ZEN_PLATFORM_WINDOWS
 #	pragma section(".zlog$a", read)
-#	pragma section(".zlog$f", read)
-#	pragma section(".zlog$m", read)
-#	pragma section(".zlog$s", read)
+#	pragma section(".zlog$l", read)
 #	pragma section(".zlog$z", read)
 #endif
 
 namespace zen {
 
-// We shadow the underlying spdlog default logger, in order to avoid a bunch of overhead
 LoggerRef TheDefaultLogger;
 
+LoggerRef
+Log()
+{
+	if (TheDefaultLogger)
+	{
+		return TheDefaultLogger;
+	}
+	return zen::logging::ConsoleLog();
+}
+
 }  // namespace zen
 
 namespace zen::logging {
 
-using MemoryBuffer_t = fmt::basic_memory_buffer<char, 250>;
-
-struct LoggingContext
-{
-	inline LoggingContext();
-	inline ~LoggingContext();
-
-	zen::logging::MemoryBuffer_t MessageBuffer;
-
-	inline std::string_view Message() const { return std::string_view(MessageBuffer.data(), MessageBuffer.size()); }
-};
+//////////////////////////////////////////////////////////////////////////
 
-LoggingContext::LoggingContext()
+LoggerRef
+LogCategory::Logger()
 {
-}
+	// This should be thread safe since zen::logging::Get() will return
+	// the same logger instance for the same category name. Also the
+	// LoggerRef is simply a pointer.
+	if (!m_LoggerRef)
+	{
+		m_LoggerRef = zen::logging::Get(m_CategoryName);
+	}
 
-LoggingContext::~LoggingContext()
-{
+	return m_LoggerRef;
 }
 
-//////////////////////////////////////////////////////////////////////////
-
 static inline bool
-IsErrorLevel(int LogLevel)
+IsErrorLevel(LogLevel InLevel)
 {
-	return (LogLevel == zen::logging::level::Err || LogLevel == zen::logging::level::Critical);
+	return (InLevel == Err || InLevel == Critical);
 };
 
-static_assert(sizeof(spdlog::source_loc) == sizeof(SourceLocation));
-static_assert(offsetof(spdlog::source_loc, filename) == offsetof(SourceLocation, filename));
-static_assert(offsetof(spdlog::source_loc, line) == offsetof(SourceLocation, line));
-static_assert(offsetof(spdlog::source_loc, funcname) == offsetof(SourceLocation, funcname));
-
 void
-EmitLogMessage(LoggerRef& Logger, int LogLevel, const std::string_view Message)
+EmitLogMessage(LoggerRef& Logger, const LogPoint& Lp, fmt::format_args Args)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
-	const spdlog::level::level_enum InLevel = (spdlog::level::level_enum)LogLevel;
-	Logger.SpdLogger->log(InLevel, Message);
-	if (IsErrorLevel(LogLevel))
-	{
-		if (LoggerRef ErrLogger = zen::logging::ErrorLog())
-		{
-			ErrLogger.SpdLogger->log(InLevel, Message);
-		}
-	}
-}
 
-void
-EmitLogMessage(LoggerRef& Logger, int LogLevel, std::string_view Format, fmt::format_args Args)
-{
-	ZEN_MEMSCOPE(ELLMTag::Logging);
-	zen::logging::LoggingContext LogCtx;
-	fmt::vformat_to(fmt::appender(LogCtx.MessageBuffer), Format, Args);
-	zen::logging::EmitLogMessage(Logger, LogLevel, LogCtx.Message());
-}
+	Logger->Log(Lp, Args);
 
-void
-EmitLogMessage(LoggerRef& Logger, const SourceLocation& InLocation, int LogLevel, const std::string_view Message)
-{
-	ZEN_MEMSCOPE(ELLMTag::Logging);
-	const spdlog::source_loc&		Location = *reinterpret_cast<const spdlog::source_loc*>(&InLocation);
-	const spdlog::level::level_enum InLevel	 = (spdlog::level::level_enum)LogLevel;
-	Logger.SpdLogger->log(Location, InLevel, Message);
-	if (IsErrorLevel(LogLevel))
+	if (IsErrorLevel(Lp.Level))
 	{
 		if (LoggerRef ErrLogger = zen::logging::ErrorLog())
 		{
-			ErrLogger.SpdLogger->log(Location, InLevel, Message);
+			ErrLogger->Log(Lp, Args);
 		}
 	}
 }
 
 void
-EmitLogMessage(LoggerRef& Logger, const SourceLocation& InLocation, int LogLevel, std::string_view Format, fmt::format_args Args)
-{
-	ZEN_MEMSCOPE(ELLMTag::Logging);
-	zen::logging::LoggingContext LogCtx;
-	fmt::vformat_to(fmt::appender(LogCtx.MessageBuffer), Format, Args);
-	zen::logging::EmitLogMessage(Logger, InLocation, LogLevel, LogCtx.Message());
-}
-
-void
-EmitConsoleLogMessage(int LogLevel, const std::string_view Message)
-{
-	ZEN_MEMSCOPE(ELLMTag::Logging);
-	const spdlog::level::level_enum InLevel = (spdlog::level::level_enum)LogLevel;
-	ConsoleLog().SpdLogger->log(InLevel, Message);
-}
-
-#define ZEN_COLOR_YELLOW	 "\033[0;33m"
-#define ZEN_COLOR_RED		 "\033[0;31m"
-#define ZEN_BRIGHT_COLOR_RED "\033[1;31m"
-#define ZEN_COLOR_RESET		 "\033[0m"
-
-void
-EmitConsoleLogMessage(int LogLevel, std::string_view Format, fmt::format_args Args)
+EmitConsoleLogMessage(const LogPoint& Lp, fmt::format_args Args)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
-	zen::logging::LoggingContext LogCtx;
-
-	// We are not using a format option for console which include log level since it would interfere with normal console output
-
-	const spdlog::level::level_enum InLevel = (spdlog::level::level_enum)LogLevel;
-	switch (InLevel)
-	{
-		case spdlog::level::level_enum::warn:
-			fmt::format_to(fmt::appender(LogCtx.MessageBuffer), ZEN_COLOR_YELLOW "Warning: " ZEN_COLOR_RESET);
-			break;
-		case spdlog::level::level_enum::err:
-			fmt::format_to(fmt::appender(LogCtx.MessageBuffer), ZEN_BRIGHT_COLOR_RED "Error: " ZEN_COLOR_RESET);
-			break;
-		case spdlog::level::level_enum::critical:
-			fmt::format_to(fmt::appender(LogCtx.MessageBuffer), ZEN_COLOR_RED "Critical: " ZEN_COLOR_RESET);
-			break;
-		default:
-			break;
-	}
-	fmt::vformat_to(fmt::appender(LogCtx.MessageBuffer), Format, Args);
-	zen::logging::EmitConsoleLogMessage(LogLevel, LogCtx.Message());
+	ConsoleLog()->Log(Lp, Args);
 }
 
 }  // namespace zen::logging
 
-namespace zen::logging::level {
+namespace zen::logging {
 
-spdlog::level::level_enum
-to_spdlog_level(LogLevel NewLogLevel)
-{
-	return static_cast<spdlog::level::level_enum>((int)NewLogLevel);
-}
+constinit std::string_view LevelNames[] = {std::string_view("trace", 5),
+										   std::string_view("debug", 5),
+										   std::string_view("info", 4),
+										   std::string_view("warning", 7),
+										   std::string_view("error", 5),
+										   std::string_view("critical", 8),
+										   std::string_view("off", 3)};
 
 LogLevel
-to_logging_level(spdlog::level::level_enum NewLogLevel)
-{
-	return static_cast<LogLevel>((int)NewLogLevel);
-}
-
-constinit std::string_view LevelNames[] = {ZEN_LEVEL_NAME_TRACE,
-										   ZEN_LEVEL_NAME_DEBUG,
-										   ZEN_LEVEL_NAME_INFO,
-										   ZEN_LEVEL_NAME_WARNING,
-										   ZEN_LEVEL_NAME_ERROR,
-										   ZEN_LEVEL_NAME_CRITICAL,
-										   ZEN_LEVEL_NAME_OFF};
-
-level::LogLevel
 ParseLogLevelString(std::string_view Name)
 {
-	for (int Level = 0; Level < level::LogLevelCount; ++Level)
+	for (int Level = 0; Level < LogLevelCount; ++Level)
 	{
 		if (LevelNames[Level] == Name)
-			return static_cast<level::LogLevel>(Level);
+		{
+			return static_cast<LogLevel>(Level);
+		}
 	}
 
 	if (Name == "warn")
 	{
-		return level::Warn;
+		return Warn;
 	}
 
 	if (Name == "err")
 	{
-		return level::Err;
+		return Err;
 	}
 
-	return level::Off;
+	return Off;
 }
 
 std::string_view
-ToStringView(level::LogLevel Level)
+ToStringView(LogLevel Level)
 {
-	if (int(Level) < level::LogLevelCount)
+	if (int(Level) < LogLevelCount)
 	{
 		return LevelNames[int(Level)];
 	}
@@ -211,17 +131,17 @@ ToStringView(level::LogLevel Level)
 	return "None";
 }
 
-}  // namespace zen::logging::level
+}  // namespace zen::logging
 
 //////////////////////////////////////////////////////////////////////////
 
 namespace zen::logging {
 
 RwLock		LogLevelsLock;
-std::string LogLevels[level::LogLevelCount];
+std::string LogLevels[LogLevelCount];
 
 void
-ConfigureLogLevels(level::LogLevel Level, std::string_view Loggers)
+ConfigureLogLevels(LogLevel Level, std::string_view Loggers)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
@@ -230,18 +150,18 @@ ConfigureLogLevels(level::LogLevel Level, std::string_view Loggers)
 }
 
 void
-RefreshLogLevels(level::LogLevel* DefaultLevel)
+RefreshLogLevels(LogLevel* DefaultLevel)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
-	spdlog::details::registry::log_levels Levels;
+	std::vector<std::pair<std::string, LogLevel>> Levels;
 
 	{
 		RwLock::SharedLockScope _(LogLevelsLock);
 
-		for (int i = 0; i < level::LogLevelCount; ++i)
+		for (int i = 0; i < LogLevelCount; ++i)
 		{
-			level::LogLevel CurrentLevel{i};
+			LogLevel CurrentLevel{i};
 
 			std::string_view Spec = LogLevels[i];
 
@@ -260,24 +180,16 @@ RefreshLogLevels(level::LogLevel* DefaultLevel)
 					Spec	   = {};
 				}
 
-				Levels[LoggerName] = to_spdlog_level(CurrentLevel);
+				Levels.emplace_back(std::move(LoggerName), CurrentLevel);
 			}
 		}
 	}
 
-	if (DefaultLevel)
-	{
-		spdlog::level::level_enum SpdDefaultLevel = to_spdlog_level(*DefaultLevel);
-		spdlog::details::registry::instance().set_levels(Levels, &SpdDefaultLevel);
-	}
-	else
-	{
-		spdlog::details::registry::instance().set_levels(Levels, nullptr);
-	}
+	Registry::Instance().SetLevels(Levels, DefaultLevel);
 }
 
 void
-RefreshLogLevels(level::LogLevel DefaultLevel)
+RefreshLogLevels(LogLevel DefaultLevel)
 {
 	RefreshLogLevels(&DefaultLevel);
 }
@@ -289,15 +201,15 @@ RefreshLogLevels()
 }
 
 void
-SetLogLevel(level::LogLevel NewLogLevel)
+SetLogLevel(LogLevel NewLogLevel)
 {
-	spdlog::set_level(to_spdlog_level(NewLogLevel));
+	Registry::Instance().SetGlobalLevel(NewLogLevel);
 }
 
-level::LogLevel
+LogLevel
 GetLogLevel()
 {
-	return level::to_logging_level(spdlog::get_level());
+	return Registry::Instance().GetGlobalLevel();
 }
 
 LoggerRef
@@ -312,10 +224,10 @@ SetDefault(std::string_view NewDefaultLoggerId)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
-	auto NewDefaultLogger = spdlog::get(std::string(NewDefaultLoggerId));
+	Ref<Logger> NewDefaultLogger = Registry::Instance().Get(std::string(NewDefaultLoggerId));
 	ZEN_ASSERT(NewDefaultLogger);
 
-	spdlog::set_default_logger(NewDefaultLogger);
+	Registry::Instance().SetDefaultLogger(NewDefaultLogger);
 	TheDefaultLogger = LoggerRef(*NewDefaultLogger);
 }
 
@@ -338,11 +250,11 @@ SetErrorLog(std::string_view NewErrorLoggerId)
 	}
 	else
 	{
-		auto NewErrorLogger = spdlog::get(std::string(NewErrorLoggerId));
+		Ref<Logger> NewErrorLogger = Registry::Instance().Get(std::string(NewErrorLoggerId));
 
 		ZEN_ASSERT(NewErrorLogger);
 
-		TheErrorLogger = LoggerRef(*NewErrorLogger.get());
+		TheErrorLogger = LoggerRef(*NewErrorLogger.Get());
 	}
 }
 
@@ -353,39 +265,75 @@ Get(std::string_view Name)
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
-	std::shared_ptr<spdlog::logger> Logger = spdlog::get(std::string(Name));
+	Ref<Logger> FoundLogger = Registry::Instance().Get(std::string(Name));
 
-	if (!Logger)
+	if (!FoundLogger)
 	{
 		g_LoggerMutex.WithExclusiveLock([&] {
-			Logger = spdlog::get(std::string(Name));
+			FoundLogger = Registry::Instance().Get(std::string(Name));
 
-			if (!Logger)
+			if (!FoundLogger)
 			{
-				Logger = Default().SpdLogger->clone(std::string(Name));
-				spdlog::apply_logger_env_levels(Logger);
-				spdlog::register_logger(Logger);
+				FoundLogger = Default()->Clone(std::string(Name));
+				Registry::Instance().Register(FoundLogger);
 			}
 		});
 	}
 
-	return *Logger;
+	return *FoundLogger;
 }
 
-std::once_flag					ConsoleInitFlag;
-std::shared_ptr<spdlog::logger> ConLogger;
+std::once_flag ConsoleInitFlag;
+Ref<Logger>	   ConLogger;
 
 void
 SuppressConsoleLog()
 {
+	ZEN_MEMSCOPE(ELLMTag::Logging);
+
 	if (ConLogger)
 	{
-		spdlog::drop("console");
+		Registry::Instance().Drop("console");
 		ConLogger = {};
 	}
-	ConLogger = spdlog::null_logger_mt("console");
+
+	SinkPtr NullSinkPtr(new NullSink());
+	ConLogger = Ref<Logger>(new Logger("console", std::vector<SinkPtr>{NullSinkPtr}));
+	Registry::Instance().Register(ConLogger);
 }
 
+#define ZEN_COLOR_YELLOW	 "\033[0;33m"
+#define ZEN_COLOR_RED		 "\033[0;31m"
+#define ZEN_BRIGHT_COLOR_RED "\033[1;31m"
+#define ZEN_COLOR_RESET		 "\033[0m"
+
+class ConsoleFormatter : public Formatter
+{
+public:
+	void Format(const LogMessage& Msg, MemoryBuffer& Dest) override
+	{
+		switch (Msg.GetLevel())
+		{
+			case Warn:
+				fmt::format_to(fmt::appender(Dest), ZEN_COLOR_YELLOW "Warning: " ZEN_COLOR_RESET);
+				break;
+			case Err:
+				fmt::format_to(fmt::appender(Dest), ZEN_BRIGHT_COLOR_RED "Error: " ZEN_COLOR_RESET);
+				break;
+			case Critical:
+				fmt::format_to(fmt::appender(Dest), ZEN_COLOR_RED "Critical: " ZEN_COLOR_RESET);
+				break;
+			default:
+				break;
+		}
+
+		helpers::AppendStringView(Msg.GetPayload(), Dest);
+		Dest.push_back('\n');
+	}
+
+	std::unique_ptr<Formatter> Clone() const override { return std::make_unique<ConsoleFormatter>(); }
+};
+
 LoggerRef
 ConsoleLog()
 {
@@ -394,10 +342,10 @@ ConsoleLog()
 	std::call_once(ConsoleInitFlag, [&] {
 		if (!ConLogger)
 		{
-			ConLogger = spdlog::stdout_color_mt("console");
-			spdlog::apply_logger_env_levels(ConLogger);
-
-			ConLogger->set_pattern("%v");
+			SinkPtr ConsoleSink(new AnsiColorStdoutSink());
+			ConsoleSink->SetFormatter(std::make_unique<ConsoleFormatter>());
+			ConLogger = Ref<Logger>(new Logger("console", std::vector<SinkPtr>{ConsoleSink}));
+			Registry::Instance().Register(ConLogger);
 		}
 	});
 
@@ -407,9 +355,11 @@ ConsoleLog()
 void
 ResetConsoleLog()
 {
+	ZEN_MEMSCOPE(ELLMTag::Logging);
+
 	LoggerRef ConLog = ConsoleLog();
 
-	ConLog.SpdLogger->set_pattern("%v");
+	ConLog->SetFormatter(std::make_unique<ConsoleFormatter>());
 }
 
 void
@@ -417,13 +367,15 @@ InitializeLogging()
 {
 	ZEN_MEMSCOPE(ELLMTag::Logging);
 
-	TheDefaultLogger = *spdlog::default_logger_raw();
+	TheDefaultLogger = *Registry::Instance().DefaultLoggerRaw();
 }
 
 void
 ShutdownLogging()
 {
-	spdlog::shutdown();
+	ZEN_MEMSCOPE(ELLMTag::Logging);
+
+	Registry::Instance().Shutdown();
 	TheDefaultLogger = {};
 }
 
@@ -457,7 +409,7 @@ EnableVTMode()
 void
 FlushLogging()
 {
-	spdlog::details::registry::instance().flush_all();
+	Registry::Instance().FlushAll();
 }
 
 }  // namespace zen::logging
@@ -465,21 +417,27 @@ FlushLogging()
 namespace zen {
 
 bool
-LoggerRef::ShouldLog(int Level) const
+LoggerRef::ShouldLog(logging::LogLevel Level) const
 {
-	return SpdLogger->should_log(static_cast<spdlog::level::level_enum>(Level));
+	return m_Logger->ShouldLog(Level);
 }
 
 void
-LoggerRef::SetLogLevel(logging::level::LogLevel NewLogLevel)
+LoggerRef::SetLogLevel(logging::LogLevel NewLogLevel)
 {
-	SpdLogger->set_level(to_spdlog_level(NewLogLevel));
+	m_Logger->SetLevel(NewLogLevel);
 }
 
-logging::level::LogLevel
+logging::LogLevel
 LoggerRef::GetLogLevel()
 {
-	return logging::level::to_logging_level(SpdLogger->level());
+	return m_Logger->GetLevel();
+}
+
+void
+LoggerRef::Flush()
+{
+	m_Logger->Flush();
 }
 
 thread_local ScopedActivityBase* t_ScopeStack = nullptr;